1. Field of the Invention
The present invention relates to a magnetoresistance effect element, a head of the magnetoresistance effect element type and a memory element and also relates to a method of producing the magnetoresistance effect element mentioned aboved.
2. Description of the Related Art
It has recently been discovered that an artificial lattice layer [Fe/Cr] or [Co/Ru] in which the magnetic layers are antiferromagnetically coupled to each other through a metallic nonmagnetic layer of Cr, Ru or the like, produces a giant magnetoresistance effect in a ferromagnetic field (1 to 10 kOe (PHYSICAL REVIEW LETTERS, Vol. No. 21, p2472-2475, 1988, PHYSICAL REVIEW LETTERS, Vol. No. 19, p2304-2307, 1990). The artificial lattice layer according to the technology above-mentioned, shows a large change in magnetoresistance (hereinafter referred to as MR). However, since the magnetic layers are antiferromagnetically coupled to each other, the magnetic field required for producing an MR effect is as big as several kOe. This is practically disadvantageous.
A giant magnetoresistance effect has been discovered also in an artificial lattice layer [Ni--Fe/Cu/Co] using two different types of magnetic layers of Ni--Fe and Co which are separated from each other through a metallic nonmagnetic layer Cu and which are weak in magnetic coupling. That is, there has been obtained an artificial lattice layer of which MR rate is about 8% in a magnetic field applied at room temperature of 0.5 kOe (Journal of The Physical Society of Japan, Vol. 59, No. 9, September,1990, pp. 3061-3064). However, even in this artificial lattice layer, it is difficult to intercept perfectly the magnetic coupling between the magnetic layers. Thus, it has been desired to develop a magnetoresistance effect element which shows a greater MR change in a smaller applied magnetic field.
When an electric current flows in the vertical direction of the layer surface, the element presents a large MR change. However, since the artificial lattice layer above-mentioned is very thin, the resistance in the vertical direction of the layer surface is very low. This is practically disadvantageous.
As an artificial lattice layer operable in a very small applied magnetic field, there is proposed a layer of the spin valve type in which an antiferromagnetic material of Fe--Mn is attached to a body of Ni--Fe/Cu/Ni--Fe (Journal of Magnetism and Magnetic Materials 93, p.101-104, 1991), and it is now studied to apply this layer to a head of the magnetoresistance effect type. However, the arrangement according to this technology is disadvantageous in view of MR change as small as 2 to 4%.
Further, there has been developed a tunnel-type magnetoresistance effect element using an insulating layer between two magnetic layers (Nihon Ohyo Jiki Gakkaishi Vol. 19, No. 2, p369-372, 1995). According to this technology, however, it is difficult to control the quality of the insulating layer. This makes it difficult to produce such elements having good reproducibility in characteristics.
There is proposed a memory element having word lines and sense lines each made of a conventional MR material (IEEE TRANSACTIONS ON MAGNETICS, VOL. 27, NO. 6, P5520-5522, 1991). This memory element is small in MR change rate such that the information reading output is disadvantageously small.
To solve the problems above-mentioned, the present invention is proposed with the object of providing a magnetoresistance effect element, a head of the magnetoresistance effect type and a memory element in each of which a larger MR change can be acquired in a smaller magnetic field, and also providing a method of producing the magnetoresistance effect element above-mentioned.